Marcell Coetzee scored the match-winning try midway through the second half after scores from Jacob Stockdale, Henry Speight and man-of-the-match Will Addison, but just as impressive as the potent Ulster attack was their defensive display, with a huge tackle count of 174 indicative of the effort put in across the squad.

The Ulstermen now sit second in the pool table on nine points, five behind leaders Racing 92 who defeated Leicester Tigers 36-26 with a bonus point. Dan McFarland's men will hope for more of the same when they host the Scarlets at Kingspan Stadium next Friday (kick-off 7.45pm).

Ireland internationals Addison and Iain Henderson made welcome returns to the starting XV in Llanelli, taking over from James Hume and Alan O'Connor respectively, while Rory Best and Stockdale, named as replacements against Cardiff Blues last Saturday, also came in as starters.

Eric O'Sullivan and Martin Moore completed the front row either side of captain Best, with last week's try scorer Kieran Treadwell partnering Henderson at lock, and a back row of flankers Sean Reidy and Jordi Murphy and powerful South African number 8 Coetzee.

In the province's back-line Louis Ludik shifted to full-back, with Speight and Stockdale on the wings, Stuart McCloskey teaming with the versatile Addison in midfield, and the half-back pairing saw Billy Burns and John Cooney combine once again.

First blood went to the Scarlets courtesy of Rhys Patchell's early penalty, but after a fine break from Speight off Addison's kick, the hosts counted themselves lucky to only concede three points when Cooney opened his account with a penalty of his own.

The warning shot went unheeded, however, and in Ulster's very next attack good footwork in midfield from Addison set Stockdale away down the left, the young winger brilliantly evading a somewhat hesitant Steff Evans and Gareth Davies on the 22-metre line before crossing for his third try of the tournament.

Cooney's conversion and a later penalty spun wide in the difficult swirling wind, but Ulster continued to dominate in both open play and set piece, and as the Scarlets' penalty count increased, the visitors made two more promising forays into the opposition 22.

The Llanelli outfit began to find their way around the 25-minute mark, Davies and Evans combining much more efficiently in attack than they had earlier done in defence, and the winger grabbing the five points after a sustained period of pressure.

Nonetheless, after Patchell converted and Nick Timoney replaced Reidy, the recipient of a bang to the head in a tackle on Lewis Rawlins, Ulster showed that their strong start had been far from a flash in the pan. The increasingly-influential Speight touched down in the right hand corner on 33 minutes after sterling work five metres out from his forwards, making it 13-10 to the province.

More of the same from Ulster as the second half began saw the visitors set up camp in the Scarlets half, eventually forcing a penalty for a collapsed 48th-minute scrum. Addison then snuck through a gap in the Scarlets defence to score off Cooney's pass after a well-executed lineout.

With the bonus point score now very much a prospect, Ulster first had to weather the inevitable Scarlets backlash, defending stoutly for a good 10 minutes - flanker Murphy finished with a haul of 22 tackles - until Best, who played a key role up front, forced a turnover from Ken Owens to buy his side some breathing space.

The Scarlets came again, however, and Evans was soon grounding the ball for his second try of the game on the hour mark, courtesy of a defence-splitting dummy from full-back Johnny McNicholl.

Only 20-17 ahead now, Ulster fully realised the need to strike back quickly, and back rower Coetzee was the man to secure the bonus point five minutes later with a dive over in the right corner after both Timoney and McCloskey had come close.

Eight points adrift with as many minutes remaining, the Scarlets threw everything but the kitchen sink at Ulster, Evans coming close to snatching his hat trick on 75 minutes only to be bundled into touch two metres from home by a combination of Speight and Ludik.

There was still time for one last raid, with replacement Dan Davis rolling over the line with mere seconds to go, and Dan Jones' successful conversion suddenly closing the gap to a single point with just enough time for a restart.

The pressure was on Ulster to see out the result and they duly did, the clock running into the 84th minute before the Scarlets were eventually stopped in their tracks for not releasing in the tackle. It all makes for a mouth-watering return to Kingspan Stadium in a week's time.

Ulster head coach McFarland commented afterwards: "I am really delighted with that tonight. Physically we fronted up and that was going to be very important. This is a difficult place to come and win, but we came wanting to play, we did and we took our chances.

"Our defence played a bit part as well, the Scarlets have a dangerous attack and we kept them at bay. Our discipline was good and that was also key. A lot of effort went in by everyone in that win and it was a great victory to be a part of."